An artificial reality system generally includes a display panel configured to present artificial images that depict objects in a virtual environment. The display panel may display virtual objects or combine real objects with virtual objects, as in virtual reality (VR), augmented reality (AR), or mixed reality (MR) applications. To interact with the artificial reality system, a user may need to provide inputs directed to at least a portion of the displayed image. Some artificial reality systems may include a dedicated input/output interface for receiving user inputs, such as hand and/or finger movements. However, traditional input/output interfaces may require frequent and active user inputs, and thus may prevent the user from having a fully immersive experience in the artificial reality environment.
An eye-tracking system can track the gaze of an artificial reality (e.g., VR/AR/MR) system so that the artificial reality system knows where the user is looking, and thus can provide a more immersive interface than a typical input/output interface predominantly reliant on a handheld peripheral input/output device. Eye-tracking may also be used for foveated imaging, foveated transmission of image data, alertness monitoring, etc. Existing eye-tracking systems may use light sources (e.g., infrared light) positioned at the periphery of the user's field of view to illuminate the eye, where the light illuminating the eye may be reflected specularly by the cornea of the user's eye, resulting in “glints” in a captured image of the eye. The position (e.g., gaze direction or rotation position) of the eye may be determined based on, for example, the location of the glints relative to a known feature of the eye (e.g., center of the pupil) in the captured image.
There may be several issues associated with existing eye tracking technologies. One of the issues is the size of the glints in the captured image for a light source that may not be a “point source.” For example, an LED which may be used as the light source may have an emission area with a diameter of 200 microns or more. Thus, when the whole LED emission area is captured, the glint may not appear as a point in the captured image. Consequently, the center location of the glint in the image may not be precisely determined, and the errors in the approximation may lead to errors in the eye tracking result. In addition, the peripheral location of the light sources may negatively impact the accuracy of the eye tracking due to, for example, the angles of the illuminating light from the light sources to the eye. While a larger number of light sources in the periphery of the user's field of view may help to increase the accuracy of eye tracking, increasing the number of light sources likely would cause a large amount of power consumption, especially for devices designed for extended use.